Giant 'sombrero' lifting Earth's crust

Researchers say satellite data has revealed a geological oddity in South America unlike any seen on Earth, a phenomenon they’ve dubbed the "sombrero uplift."

At the border of Argentina, Bolivia and Chile lies the Altiplano-Puna plateau in the central Andes region, home to the largest active magma body in Earth’s continental crust.

Researchers at the Scripps Institution of Oceanography at the University of California, San Diego, say magma is forming a growing blob under the Earth’s crust, pushing up Earth’s surface across an area 62 miles wide while the surrounding area sinks.

The unique geological phenomenon resembles the shape of a Mexican hat, leading researchers to describe it as the "sombrero uplift."

"It’s a subtle motion, pushing up little by little every day, but it’s this persistence that makes this uplift unusual," UC Davis geophysics Professor Yuri Fialko said. "Most other magmatic systems that we know about show episodes of inflation and deflation."

The steady motion and sombrero-shaped deflection is likely being caused by a large blob of magma, geologically known as a "diapir," forming on top of the Altiplano-Puna magma body, researchers said.

Diapirs have been studied using geologic records in rocks frozen many millions of years ago, but the new study is the first to identify an active magma diapir rising through the crust at present day, a UC Davis release said Thursday.